The invention relates generally to insulated roof structures and more particularly to a roof insulation support for a metal building.
In the construction of metal buildings, generally a plurality of transversely extending main roof support beams are provided for defining a peaked, sloped or flat roof. These transversely extending main roof support beams support a plurality of longitudinally extending purlins, the purlins being arranged in a generally parallel array. The purlins are of a channel or Z-shaped cross section and are usually provided with a longitudinally extending upturned lip disposed on the bottom of the purlin. The lower surface of the purlins is firmly secured to the transversely extending beams. Metal roof panels forming the exterior surface of the roof are then secured to the tops of the purlins.
These types of metal roof building structures have been insulated by a number of prior art arrangements. For example, it is not uncommon for a layer of rolled insulation and/or a layer of rigid closed cell foam insulation to be laid over the tops of the purlins before the metal roof panels are secured thereto. Problems with this roof insulating arrangement stem from the fact that the batts or rivets that are used to secure the metal roof panels to the purlins provide a thermal "short circuit" causing the purlins to be in good thermal conductivity with the exterior surface of the building. In addition to increasing heating and cooling costs, in the winter condensation of moisture on the purlins can become a problem. Other problems with this type of roof insulation include difficulty providing a layer of insulation of sufficient thickness to achieve the high insulation factors desirable with todays high energy costs and difficulty in upgrading the insulation factor of existing insulation of this type.
It has also been known to secure roof liner panels to the bottoms of the purlins with bolts, rivets, or the like and to fill the space between the roof liner panels and the metal roof panels with fiberglass insulation or the like. However, the process of attaching the roof liner panels to the lower flanges of the purlins by means of rivets or screws is a very time consuming one, resulting in high labor costs. Thus, a variety of prior art roof insulating systems evolved, employing longitudinally extending roof liner panel hangers which are provided with resilient clips for gripping the bottoms of the purlins. These hangers are generally provided with an inverted T-shaped cross section defining a bottom flange upon which the roof liner panels rest. The roof liner panels extended between adjacent hangers and, in some cases where the distance between hangers is great, transversely extending beams, also supported by the hanger flanges, are disposed between adjacent roof liner panels. These transversely extending beams are also provided with T-shaped cross sections to define lower flanges for supporting the transversely extending edges of the roof liner panels.
While this latter type of roof insulation support system is easier to install then systems involving the attachment of roof liner panels with screws, rivets or the like, and in fact, this system can be retrofitted on an existing building structure, the resilient clips of prior art hangers often do not fit purlins of varying thickness or accommodate sections of the roof structure where the purlins were overlapped. In cases where the distance between purlins is great and additional support for the roof liner panels is provided by transverse beams, installation is made awkward by the poor torsional stability of the beams. The torsional stability of the transversely extending beams is important since if a transversely extending beam rotates during installation of the panels, a tight pack of the panels will not be achieved. Also, the poor torsional stability of the beams makes reentry into the insulated space for maintenance on pipes and other fixtures in the insulated space difficult since removal of one or more of the panels may loosen the packing of the panels, allowing one or more of the beams to rotate as the panels are manipulated. The poor torsional stability of the transversely extending beams hamper installation of the beams and made reentry into the insulated space somewhat more tedious.